Session: 04-02-02: Advances in Aerodynamics & Novel Aerospace Propulsion Systems

Paper Number: 70495

Start Time: Tuesday, 10:15 AM

70495 - Effect of Self-Actuating Flap on the Aerodynamic Performance of Flat Plate Wing at Low Reynolds Number 

The Reynolds number is a key parameter for the development of small-scaled air vehicles like micro unmanned air vehicle (μUAVs), micro air vehicles (MAV), Nano air vehicles (NAVs), etc. But due to their limited wing size and power input, such aircraft operate under a very low Reynolds number range (10⁴ – 10⁶). The major problem for these aircraft is flow separation which occurs at a lower angle of attack and leads to a sudden decrease in the lift. The method discussed here considers flap for the flow control by delaying flow separation. This technique is inspired from the bird flights. It has been observed in birds that, the upper side of feathers come up during their landing to control the flow separation over the wing. Similar action is planned for the improvement of the aerodynamic coefficients of a flat plate wing in the present studies. Herein, two wing models of aspect ratio 1 and 2 are chosen for the experiments. These models have same chord length 150 mm but different span sizes as 150 mm and 300 mm respectively. The flap, used as a lift enhancement device, is mounted on the suction surface of the wing. It is made of a Mylar sheet of thickness 0.35mm and width of 20% of chord length (0.20c). Present mounting allows the flap to rotate freely about its leading edge without supply of any external energy. This flap is mounted at two locations ( 60% of chord, 70% of chord) on the upper surface of the wing. All the experiments are performed in an open circuit low-speed wind tunnel established at IIT Guwahati, India, for the chord-based Reynolds number range of 10⁴ -10⁶. It has been observed, the flap remains attached to the wing surface at low angles of attack. But, as the angle of attack increases, flow separation begins to occur along the trailing edge which lifts ups the flap and adjusts itself in a situation so that the flow reattaches. Hence, the lift curve, for pre-stall angles is almost identical in both clean and flapped configurations. Further, both the flap locations are seen to improve the lift coefficient than the clean airfoil for post-stall angles. Details of the experiments, analysis of results, and effectiveness of a flap will be discussed in the full-length paper.

Keywords: Subsonic wind tunnel, Low aspect ratio wings, Aerodynamic force measurement, Self- actuating flap.

Presenting Author: Anand Verma IIT Guwahati

Authors:

Anand Verma IIT Guwahati
Vinayak Kulkarni IIT Guwahati